Multi stage thermoelectric power generation using an ammonia absorption refrigeration cycle and thermoelectric elements at numerous locations in the cycle

ABSTRACT

A thermoelectric generator system including a refrigerator of the of the absorption type having no moving parts and operating with ammonia, water and hydrogen to extract heat from a heat source and discharge heat from an absorber and having at least one thermocouple positioned to intercept heat flow from the heat source to the boiler and/or from the condenser to the evaporator. The system is arranged such that a boiler from one system absorbs heat discharged from the absorber of one or more other identical systems so that systems can be ganged together to produce a combine system having increased efficiency.

CROSS REFERENCE TO OTHER APPLICATIONS

This application is a continuation in part of application Ser. No.08/491,787 filed Jun. 19, 1995 now abandoned.

FIELD OF THE INVENTION

This invention relates to a thermoelectric power generation system thatemploys an absorption refrigeration cycle to increase Carnot efficiencyof converting heat from fuel to electricity.

BACKGROUND

The Peltier effect is a thermoelectric effect demonstrated by referenceto FIG. 1 (prior art) showing a thermocouple of two dissimilarconductors, 10 and 12, joined at one junction 14 maintained attemperature T' by reservoir 18 and joined at a second junction 16maintained at a lower temperature T" by reservoir 20. If conductor 10 isbroken and a motor 22 is connected to the thermocouple, then an electriccurrent I will flow through each conductor and a back EMF (E) across themotor terminals will be generated such that

    EI=Π'I-Π"I

EI is the work performed by the motor 22. ΠI represents heat fromreservoir 18 flowing into the thermocouple at the first junction 14 andΠ"I represents heat flowing into reservoir 20 out of junction 16. The"Peltier" coefficients Π' and Π" have values characteristic of thematerials at temperatures T' and T" respectively. The Peltiercoefficient of each junction is a function of temperature governed by:

    Π/T=dE/dT.

Factors which diminish the efficiency of the thermoelectric powergenerator of FIG. 1 include joule heating and the Thompson effect. TheThompson effect is the efflux or influx of heat in a conductorconducting an electric current simultaneously with the presence of athermal gradient in the conductor. In the foregoing discussion, theThompson effect has been neglected.

Another important factor that limits the efficiency of thethermoelectric power generator of FIG. 1 is the rate with which thereservoir 18 supplies heat to the junction 14 and the rate with whichjunction 16 supplies heat to reservoir 20. This rate can be limited, forexample, by thermal conductivities of the media of reservoirs 18 and 20which reduce the thermal gradient between junctions 14 and 16. Anotherconsideration is that, while a large thermal gradient between thejunctions generates a greater Peltier potential, it also results inincreased heat being conducted through the junction and dissipated bythe heat sink.

The net effect of factors leading to thermal losses is that, as thetemperature difference across the thermoelement is increased, theadvantage of increased thermopotential due to the increased differenceof work functions is offset by a greater increase of thermal losses dueto, for example, photon and phonon vibrations, etc.

According to the present state of the art, the most efficientthermoelectric materials are semiconductors such as lead telluride,silver gallium telluride, copper gallium telluride, silver indiumTelluride, silver gallium telluride, copper gallium telluride, sodiummanganese telluride. Compounds of Selenium, for example silver antimonySelenide and of sulfur, for example, the rare earth sulfides, exhibitstrong thermoelectric properties. Compounds containing at least onemember of the group selenium, sulfur and tellurium are known aschalcogenides. Small amounts of various agents (doping agents) such asindium or sodium may be incorporated in the thermoelectric compositionsto establish the type of conductivity (p or n) of the material) The mostcommercially common pn materials used for electrical power generationare either Bismuth Telluride or Lead Telluride.

Those materials which are the primary materials used to generateelectrical power according to the present state of the art, all havepoor Carnot efficiencies. in converting fuel into electricity. TheCarnot efficiency of present thermoelectric materials in commercialelectrical generation systems as a whole never exceed 6%. (Somemanufacturers claim 8-9% for n type lead telluride but this claim is nota system claim but a claim for a single material standing alone.)because of the low Carnot efficiency, thermoelectric devices are notemployed for generating electricity for utility purposes.

Thermoelectric generation of power using p n materials is generallyemployed only under conditions where reliability is a greater concernthan energy efficiency. A typical commercial bismuth tellurideelectrical generator has a thermopile between a gas driven burner and aset of cooling fins exposed to ambient temperature. The temperature ofgas (air) carrying exhaust heat emitted from a well designed commercialthermoelectric generator is ideally very near the temperature of thecooling fins. Nevertheless, the present state of the art generator ischaracterized by substantial loss of heat such that the efficiency isabout 6%.

According to practices of the present art, heat generated bythermoelectric devices that was not used to generate thermoelectricitywas either used directly for such purposes as to heat water or a room orwas wastefully exhausted.

For example, some manufacturers of hot water heaters have placed athermopile (generally thermal piles made of bismuth telluride) between aheat source (produced by a flame) and the water that is to be heated.This was an attempt to use all the heat to warm water that was not usedto produce thermoelectricity.

The principle of the Carnot cycle which applies to the devices discussedabove is to extract energy as heat, Q₂, from a source at a temperatureT₂, apply a a portion of the energy to performance of work, W, anddischarge the remainder, Q₁ =Q₂ -W at a lower temperature. T₁. Accordingto the well known Carnot principle, the maximum efficiency, E=W/Q₂ thatcan be achieved from a carnot engine operating between temperatures T₁and T₂, is::

    E.sub.max =(T.sub.2 -T.sub.1)/T.sub.2 (The Carnot efficiency)

The objective in operating a refrigerator is to perform work to withdrawheat Q₂ ' from a source at temperature T₂ ' and to discharge the heat Q₂' to a heat sink at temperature T₁ ' where T₁ >T₂. This requiresperforming an amount of work W which is equivalent to an additionalamount of heat discharged to the heat sink so that the total amount ofwork discharged to the heat sink is Q₁ ' where:

    Q.sub.1 =Q.sub.2 +W

A typical absorption refrigerator system circulates a solutioncontaining two components which have different boiling points. A commonsolution for this type of refrigeration is ammonia dissolved in water. Agas flame heats the solution of ammoniated water to chive off gaseousammonia. The ammonia gas is then cooled in a condenser to ambienttemperature and condenses to a liquid. The heat of condensation isexpelled to the ambient environment. The liquid ammonia is thendischarged into an evaporator where it evaporates and therefore absorbsheat so as to produce a cooling effect. Hydrogen gas is present in theevaporator and mixes with the ammonia thereby ballasting the pressurethroughout the system. The heavy ammonia vapor mixed with hydrogen isthen conducted to an "absorber" where the ammonia is absorbed byincoming water and the hydrogen is expelled. The ammonia dissolving inthe water generates heat and this heat of solution is allowed todissipate from the absorber in order to maintain the temperature of thewater ammonia solution at ambient temperature and ensure that the wateris saturated with ammonia at room temperature. Then the ammonia-in-watersolution circulates back to the location of the flame where ammonia isdriven off by the heat of the flame and the cycle is repeated. For amore detailed description of the absorption refrigerator, the reader isreferred to "Heat and Thermodynamics" by Zemansky published by McGrawHill, New York, N.Y. 1943 pages 211-214 which is hereby incorporated asreference into this specification.

All of the generating and refrigerating devices of the present artdescribed above discharge large amounts of waste heat.

THE INVENTION

Summary::

It is an object of this invention to provide an efficient electricalgeneration system by using refrigeration principles to direct heat fluxthrough one or more thermoelectric devices that would otherwise be lostas heat exhaust in conventional devices.

In one embodiment, a first thermopile is positioned between the gasflame and the boiler unit of an absorption refrigerator so that part ofthe heat flux generated by the temperature gradient between the flameand the boiler is used to generate thermoelectric power in the firstthermopile. The second thermopile has its high temperature side exposedto an air current that has been positioned to draw heat from theabsorber and condenser. and its low temperature side cooled bypositioning proximal to the evaporator.

In another embodiment, the invention comprises a unit that includes anabsorber refrigerator and a one or more thermopiles where the units areganged together in succession such that heat exhausted by one unit ispassed onto a successive (lower stage) unit. Each stage is characterizedas operating in a temperature range that is lower than the precedingstage and higher than the following stage. The thermopile of each unithas a "high temperature side" maintained at an elevated temperature bycontact with the condenser of the absorption refrigerator and whose "lowtemperature side" is cooled by contact with the evaporator side of thesame refrigerator. Each stage may have more than one unit and any stagemay have fewer units than a next higher stage corresponding to a heatflow through the system that diminishes due to the generation ofthermoelectric power as the heat flows from one stage to the next stage.

The efficiency of the system of units ganged together in stages residesideally in the fact that the heat escaping from one stage is used toproduce thermoelectricity in the following stage so that the heatexpressed at the last stage is substantially reduced from the heatentering the first stage in contrast to devices of the present art. Thesystem is amenable to using the presently known most efficientthermoelectric materials.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates the Peltier effect.

FIG. 2 shows one embodiment of the thermoelectric power generatingsystem of the invention.

FIG. 3 shows another embodiment of the system with a circulating fan andan additional thermoelectric pile.

FIG. 4 shows a thermoelectric generator unit of the invention.

FIG. 5 shows four units of FIG. 3 ganged together.

FIG. 6 shows an arrangement for ganging together more than one unit perstage.

FIG. 7 shows alternate locations for positioning the thermopile within astage.

FIG. 8 shows shows alternate locations for positioning the thermopilebetween stages.

DESCRIPTION OF A PREFERRED EMBODIMENT

Turning now to a discussion of the drawings, FIG. 2 shows one embodimentof this invention for converting heat to thermoelectric power..

There is shown a boiler 11 for heating a solution of ammonia and water.The solution contained in the boiler 11 is forced up through line 17 toseparator 13. In this embodiment, the boiler has a temperature of about70° Celsius.

A first thermopile 21 is positioned such that the thermal high side isin thermal contact with the burner 24 and the thermal low side is thetop side in thermal contact with the boiler 11. A thermopile containingbismuth telluride is preferred which produces 1.65 volts at 14 watts.

The heated solution then passes to separator 13 where ammonia vapor goesout line 30 to condenser 31. and water goes out conduit 34 joiningconduit 35 back to absorber 36.

In absorber 36, ammonia mixed with hydrogen coming through line33 fromevaporator 27 recombines with water and the recombined water and ammoniago back on line 25 to boiler 11 while hydrogen escaping from thecombined water and ammonia goes on line 35 to the evaporator 27.

FIG. 2 shows a source of hydrogen 32 with a valve 39 for admitting acontrolled amount of hydrogen into the conductor 33. FIG. 2 also shows apump 23 (fan) for aiding circulation of hydrogen separted from theamonia and water in the absorber 36 back to the evaporator 27.

In evaporator 27, liquid ammonia from the line 42 leading from condenser31 vaporizes as it mixes with hydrogen gas returning from the absorptionunit 36.

A second thermopile 28 is shown whose thermal high side absorbs heatfrom air circulating through line 19 that is used first used to coolcondenser 31, then cools absorber 36 and finally passes in contact withboiler 11.. The thermal low side of second thermopile 28 is conjunctswith the evaporator 27.

A cowling 29 is shown around condenser 31. The air through line 19 isheated when air fan 45 draws cooling air passing through cowling 29 andcowling 41 around absorber 36 then through a junction box 38 which drawshot air from burner 24. The junction box 38 can thus be used to shuntthe incoming air from the condenser 31 and the absorption unit 36 firstthrough the flame and then into the line 19 taking heat to the thermalhigh side of the second thermopile 28

The invention combines the traditional thermoelectric material having ahigh thermoelectric potential but a low efficiency of power conversionwith the refrigeration principle to produce a system having a secondtemperature potential or difference to drive a second thermopile made upof traditional thermoelectric materials

The invention thereby invokes the refrigeration principal to apply heatdischarged in establishing a temperature gradient across a firstthermopile to drive a second thermopile.

Example of embodiment 1.:

The gas flame from burner 24 boils and agitates a solution of ammoniaand water in boiler 11 so that a portion of the solution flows throughthe line 17 into separator 13. In so doing, more than 90% of the heatproduced by the flame is conducted through the first thermopile 21 About6% of the heat flux passing through thermopile 2 1c produces 14 watts ofelectricity at 1.65 volts. The ammonia in the evaporator 27 undergoes aliquid to vapor phase change and in so doing absorbs more than 315calories of heat per gram. Water flows out from the separator 13 to theabsorber 36 via line 34 connected to another line 35 that is the returnpath for the hydrogen. The vaporized ammonia in the separator 13 goesthrough line 30 leading to condenser 31 where the ammonia gives up morethan 315 calories of heat per gram that the ammonia absorbed at boiler11. The liquid ammonia continues in line 42 (an extension of line 30) toevaporator 27. Here the ammonia is subjected to negative pressure due tothe absorber 36 recombining ammonia and water. Because of this, ammoniaagain absorbs more than 315 calories per gram in the transition formliquid to gas. This produces a cooling effect which draws heat through asecond thermopile 28 that is receiving part of its heat from ambient airthat has been prewarmed by heat from condenser 31 and heat transfer fromexhaust gases from the burner 24 through an air moving system composedof cowling 41, air lines, 16 and 20 and a fan 5 (2-3 watts). The airmoving system also draws heat from the absorption unit 36 that is drawnoff by cowling 41 connected to air line 20. The vaporized ammonia thencombines again with water in the absorber 36 via connecting line 13. Theaccompanying hydrogen leaves the absorber 36 via return line 15. thesame return line 15 delivers water separated in separator 13.

The second thermopile 28 thus converts to electrical energy a portion ofenergy not converted to electrical energy by the first thermopile 21.Using current thermoelectric materials, the amount of electrical energyconverted by each thermopile is below 8% of the total available energywhereas the amount of electrical energy converted by the combinedthermopiles of the present invention is about 14%.

In the foregoing example, the ammonia-water solution of the system hasbeen designed to boil at about 70° Celsius (ambient temperature) so thatthe condenser cooling fins of the ammonia and water absorptionrefrigerator has a temperature of 70° Celsius. The exhaust gas isemitted at a a temperature a few degrees over 70 degrees Celsius. Thethermopile produces about 14 watts at 1.65 volts. The system alsoproduces about 20 or more watts of cooling power. Because of theinefficiency of the burner, 20 or more watts of heat energy does not gothrough the thermopile. This energy is routed to the high temperatureside of the second thermopile 28 while the cooling power is expressed onthe low temperature side of the second thermopile 28. electrical outputof the second thermopile is just over 10 watts. The effect of this isthat using state of the art thermopiles that have a 6% Carnot efficiencyfor converting fuel into electricity can approach an overall systemefficiency of up to 10% (or more) Carnot efficiency by adapting therefrigeration technique of this invention.

The invention retains the advantages characteristic of thermoelectricpower generation of having no moving parts in the actual generationprocess. The fan is only an added feature which aids in moving the airand may be eliminated for a passive air moving system to move the warmair past the high temperature side of the second thermopile.Furthermore, non-induction motors that have long life expectancies andhigh reliability of thermoelectric generators can be employed where afan will be more advantageous. The invention offers the traditionalreliability of, thermoelectric generators that have no moving parts forapplications at remote sites such as cathodic protection of pipe lines,power sources for communication devices and metering measuring devices.A further advantage of the invention is that it converts fuel much moreefficiently than devices of the prior art.

The foregoing description discloses a generator system having twothermopiles with one heat source to drive two thermoelectric piles. Itis another embodiment of the invention that a third thermopile can beadded as shown in FIG. 3. FIG. 3 shows the thermoelectric generatorsystem of FIG. 2 with components indicated by numerals corresponding toFIG. 2. In addition, condenser 31 heats a third thermoelectric pile 44which has its low side in heat conducting proximity to an evaporator 47of a second adsorption refrigeration system 46 whose condenser 48 isjoined in a thermal path through a fourth thermopile 49 to theevaporator 27 of the first system

Additional thermoelectric piles and accompanying refrigeration systemscan thus be cascaded together up to a practical limit depending on thetemperature of the heat source.

FIG. 4 shows a thermoelectric power generator unit that can be gangedwith other identical units as illustrated in FIG. 5 FIG. 4 shows aboiler 54, which receives a solution of ammonia in water gravity fedfrom an absorber 56 through line 52 and is heated from an outside source(outside source not shown in FIG. 4) The heated solution passes on line57 to a separator 53 where ammonia gas escapes on line 60 to condenser61. The condensed ammonia gas proceeds to evaporator 51 where itevaporates and mixes with hydrogen coming from absorber 56 on line 58.Water returned to the absorber 56 on line 55 from the separator 53 isheated by absorbing ammonia from the hydrogen-ammonia mix. Absorption ofthe ammonia also reduces the partial pressure of the ammonia in theevaporated and thereby promotes evaporation of the ammonia in theevaporator. Hydrogen separated from the ammonia gas by absorption of theammonia by water returns to the evaporator where it ballasts thepressure throughout the system and establishes the equilibrium partialpressure of the ammonia gas.

A thermopile 68 is placed between the condenser 61 and the evaporator 59so that the temperature gradient between the condenser 61 and evaporator59 generates thermoelectric power in the thermopile. The amount ofhydrogen in the absorber-evaporator maintains the boiling temperature ofthe ammonia in the evaporator at a temperature sufficiently less thanthe temperature of the ammonia condensing in the condenser therebyestablishing the temperature gradient across the thermopile so as todrive the thermopile. The temperature in the absorber 56 is less thanthe temperature of the boiler 54 which is necessary in order that heattaken in by the boiler 54 at one temperature from an upper stage (notshown) is delivered to the lower stage (not shown in FIG. 4) by theabsorber 6. minus heat extracted by the thermopile. 8. The difference intemperature between the absorber 56 and boiler 54 also ensures thatwater at the lower temperature of the absorber is saturated with ammoniawhich is then driven off by the heat of the boiler 54.

The partial pressure of hydrogen is maintained by the volume of hydrogenmaintained in the absorber-evaporator lines 28 and 15) and the gasmoving device 6 5 (fan) which moves the ammonia-hydrogen mixture fromthe evaporator 59 through line 66 to the absorber 56 and thereby forcesthe hydrogen (stripped of ammonia by the absorber 56) passes back online 59 back to the evaporator 51.

Summarizing the function of the thermogenerator unit of FIG. 4, heat istaken in by the boiler 54 from an "upper" sttage source. The upper stagesource may be the absorber of another thermoelectric generator or a"primary" source such as a motor. Part of the heat is extracted as powerby the thermopile. The rest of the heat absorbed is discharged by theabsorber to the boiler of the "lower" stage thermoelectric unit.

FIG. 5 shows the primary heat source 70 to be body of warm water at atemperature of 98° delivering heat to a heat sink 72 at 48° celsiusthrough four thermoelectric units 50 of this invention.

FIG. 6 shows an arrangement in which the "boiler" of the unit 50(cutaway) of one stage is a tube 74 passing through two absorbers 54 ofa next higher stage. In this manner, each successive stage may havefewer units .thereby concentrating the heat passing from stage to stageas the operating temperatures of each stage is reduced due to theproduction of thermoelectric power in each stage..

Variations and modifications of this invention may be suggested byreading the specification and studying the drawings which are within thescope of the invention.

For example, FIG. 1 shows a fan 23 in the hydrogen line 15 forcirculating hydrogen.

Thermoelectric piles may be positioned at other locations.

FIG. 7 shows a thermoelectric pile 74 having the evaporator 50 on oneside and the other side on the water absorption unit 56. FIG. 7 alsoshows a thermoelectric pile 76 having one side communicating with thecondenser 61 and second side communicating with a means of heatrejection which is shown to be the atmosphere but which could also be acooling system. FIG. 8 shows a thermoelectric pile 78 of having its highside communicating with the condenser 61A of stage 50A and its low sidecommunicating with the boiler 54B of stage 50B.

Sources of thermal energy other than combustible fuel may be used todrive the generation system. Other sources could include nuclear energyand geothermal energy.

Other components undergoing phase changes other than liquid-gas phasechanges may be used to transfer heat from a heat source

In view of these and other variations and modifications, I thereforewish to define the scope of my invention by the appended claims.

What is claimed is:
 1. A thermoelectric generator system for convertinga portion of heat flowing from a heat source to electricity whichcomprisesa boiler means (11) adapted to have thermal contact with saidheat source for heating a liquid solution of a first component and asecond component; a separator means (13) communicating with said boilermeans (11) such that when said solution is heated by said heat from saidsource (24), said liquid solution passing into said separator means (13)is separated into liquid first component and gaseous second component;an absorption means (36) for mixing said first and second components andexhausting heat of solution generated by mixing said first and secondcomponents; first conduit means (35) for conducting said first componentfrom said separator means (13) to said absorption means (36); acondensing means (31) for condensing said second component from agaseous second component to a liquid second component; a second conduitmeans (30) for conducting said gaseous second component from saidseparator means (13) to said condenser means (31) whereby said gaseoussecond component is condensed to a liquid second component; anevaporator means (27) communicating with said condenser means (31) forconverting said liquidus second component to gaseous second component; athird conduit means (33) for enabling said evaporator means (27) tocommunicate with said absorption means (36) such that said gaseoussecond component passes from said evaporator means (27) to saidabsorption means (36) and mix with said liquid first component meansreturning from said separator means; at least one thermopile means forgenerating thermoelectricity, each of said at least one thermopilehaving a first surface and a second surface where a portion of heatflowing into said first surface and out of said second surface isconverted to the thermoelectricity; any one of said at least onethermopile being located in any one of:(i) a first position where saidfirst surface is in thermal contact with said source of heat and saidsecond surface is in contact with said boiler whereby heat flows fromsaid source of heat through said thermoelectric pile to said boilerwhereby thermoelectricity is generated in said thermoelectric pile; (ii)a second position where said first surface is in thermal contact withsaid condenser means and said second surface is in contact with saidevaporator means whereby heat flows from said condenser means throughsaid thermoelectric pile to said evaporator means such as to generatethermoelectricity in said thermoelectric pile; (iii) a third positionwhere said first surface is in thermal contact with said absorptionmeans and said second surface is in contact with said evaporator meanswhereby heat flows from said absorption means through saidthermoelectric pile to said evaporator means such as to generatethermoelectricity in said thermoelectric pile; (iv) a fourth positionwhere said first surface is in thermal contact with said condenser meansand said second surface is in contact with means for removing heat fromsaid system whereby heat flows from said condenser means through saidthermoelectric pile and out of said system such as to generatethermoelectricity in said thermoelectric pile.
 2. The system of claim 1which comprises a fifth conduit means (16) for circulating air from alocation (29) proximal to said condenser means (31) to a location (21)proximal to said absorption means (36) to a location (38) proximal tosaid burner means (24) and thence to a location proximal to said firstsurface of said at least one thermocouple means (28).
 3. The system ofclaim 2 which comprises means for ballasting pressure between saidevaporator means and said absorption means.
 4. The system of claim 3wherein said ballasting means comprises:means for introducing acontrolled amount of a gaseous third component into said third conduitmeans (33); a fourth conduit means (35) for conducting said thirdcomponent from said absorption means (36) to said evaporator means (27).5. The system of claim 4 wherein said fourth conduit means comprises apump means (23) for pumping said gaseous third component through saidfourth conduit means from said absorption means to said evaporator means(27).
 6. The system of claim 1 wherein said at least one thermopilemeans comprises lead telluride.
 7. The system of claim 1 wherein saidthermopile comprises bismuth telluride.
 8. The system of claim 1 whereinsaid first component is water.
 9. The system of claim 1 wherein saidsecond component comprises ammonia.
 10. The system of claim 4 whereinsaid third component is hydrogen.
 11. The system of claim 1 wherein saidheat source is a combustible fuel.
 12. The system of claim 1 whereinsaid heat source is selected from a group of sources which consists ofsources of solar energy, energy from catalytic conversion of a fuel,nuclear energy, geothermal energy.
 13. A thermoelectric power generationsystem which comprises:a plurality of thermoelectric power stageswherein each stage includes:(i) a boiler means having a first locationand adapted for absorbing heat from a source of heat at said firstlocation; (ii) said boiler means adapted for holding a liquid solutionof a first component and a second component; (iii) a separator meanscommunicating with said boiler means such that when said solution isheated by said thermal energy, said liquid solution passes into saidseparator means where said second component is separated as a gas fromsaid liquid first component; (iv) an absorption means for mixing saidfirst and second components whereby a liquid mixture of said first andsecond components is formed; (v) first conductor means for conductingsaid first component from said separator means to said absorption means;(vi) a condensing means for condensing said second component from agaseous second component to a liquid second component; (vii) a secondconductor means for conducting said gaseous second component from saidseparator means to said condenser means whereby said gaseous secondcomponent is condensed to liquid second component; (viii) an evaporatormeans communicating with said condenser means for converting saidliquidus second component means to gaseous second component means; (ix)a third conduit means connecting said evaporator means and saidabsorption means such that said gaseous second component passes fromsaid evaporator means to said absorption means; (x) a fourth conduitmeans adapted for conducting a gaseous third component from saidabsorption means to said evaporator means; (xi) means for introducing apredetermined amount of a gaseous third component into one of:(a) saidthird conduit means; (b) said fourth conduit means; such that saidpredetermined amount of said third component is selected to ballastpressure in said evaporator and absorber means; (xii) a pump meansconnected to said fourth conduit means adapted for pumping said gaseousthird component from said absorption means to said evaporator means; ahigh end stage of said plurality of stages having said respective boilerhaving a first location adapted to be in thermal contact with saidsource of heat; said plurality of stages being serially connected in asuccession of said stages beginning with said high end stage connectedto a neighboring stage such that each stage has one of:(i) a respectivecondenser; (ii) a respective absorber; in thermal contact respectivelywith said respective boiler of another neighboring stage and ending witha low end stage having a respective condenser in thermal contact with aheat sink whereby heat flows from said source of heat through saidsystem and is discharged to said heat sink.